Ok why are you letting your nitrates build up?
I totally feel your pain, I have battled all sorts of pests and algae, it ain't fun (dinos just about did me in). For me, the answer was to remove the sandbed. Not sayin that thats your answer but it certainly fixed a lot of my issues. Then again, I just have different issues now. Moved and lost stuff, MH bulb broke and fried half my tank.
I dunno, sometimes I wonder if it weren't for the "challenges" if this hobby would be near as "interesting". Then again some challenges are too much for some. At this point I keep doing the "I've got so much invested I'm not going to let this hobby beat me" attitude. I'm going to win dammit!!
